There is known a car navigation apparatus having a route guide function to a destination. Generally, when a user designates a destination, the route to the destination is calculated, and a guide route is determined. When a vehicle of the user approaches the guide point on the guide route, guide information indicating a right/left-turn at the guide point is presented by a display on a display screen and a sound guidance (see Patent Reference 1, for example).
Generally, the route guide is executed by two methods, i.e., a guide on a display screen and a guide with a sound. In the guide on the display screen, the guide route is indicated in a specific color on a map screen, and an enlarged intersection map is displayed thereon, for example. In the guide with the sound, such a sound message as “GO STRAIGHT AHEAD 100 M, AND TURN TO THE RIGHT” is reproduced in front of the intersection, for example.
However, in the normal navigation apparatus, even when no navigation screen is displayed on a display device during displaying a sound list of a reproduced CD, the normal route guide is executed. Namely, even when no guide is executed on the display screen, the route guide is executed in the method determined by assuming that both of the guide on the display screen and the guide with the sound are executed. Therefore, the route which is actually impossible to drive only with the guide sound is sometimes guided. For example, even if the guide only with such a sound as “GO THE SIDE ROAD SOON. AFTERWARD, GO IN THE OBLIQUE DIRECTION” is executed, it is very difficult to travel as guided without the guide on the display screen.
As such a case that no navigation screen is displayed on the display device, there are such a case that a monitor in an in-dash type is stored in a main body and such a case that a monitor is not connected to a navigation apparatus including the attachable and detachable monitor, other than the above example. However, those cases are similar.
Patent Reference-1: Japanese Patent Application Laid-open under No. H11-83524